This invention relates to a distance detecting device for a camera, and more particularly to a drive signal generating circuit for an active type distance detecting device.
As cameras have been automated, it has been more popular to incorporate a distance measuring device into a camera body.
Distance measuring device incorporated in cameras are commonly classified into two groups including a passive type wherein a focused point of time is detected based on detection of coincidence of double images or dimming and an active type wherein light is irradiated from a light emitting element onto an object and a focussed point of time is detected depending upon a change of reflected light from the object. The latter active type is advantageous for a distance detecting device for a camera in that it is simple in construction and and besides it can effect measurement of a distance independently of brightness of the object.
However, the active type requires driving of a light emitting element in synchronized relationship with scanning of a distance measuring optical system. Accordingly, the active type has drawbacks that since drive currents for the distance measuring optical system and the light emitting element overlap each other, a large load electric current becomes necessary, resulting in acceleration of consumption of a cell, and besides high noises are produced due to a rapid change.